Magnetron

ABSTRACT

A magnetron includes an oscillating section having an electron radiating cathode and a cylindrical anode; an output section having an antenna inserted therein; and a pair of doughnut-shaped magnets disposed one on the end surface of the anode and one on the other end surface thereof in a manner to be coaxial with the anode. Between the end surfaces of the oscillating section and the magnets a pair of shim plates are arranged. The shim plate has a plurality of projections point-contacted with the magnet.

Unite States Patent 1191 Koinuma May 7, 1974 MAGNETRON 3,465,201 9/1969 Dorgelo 315/3971 [75] Inventor: Tokujo Koinuma, Kawasaki, Japan Primary Examiner-Arch1e R. Borchelt [73] Ass1gnee: Tokyo Slnbaura Electric Co., Ltd., Assistant Examiner saxfield Chatmon In Kawasakl'shh Japan Attorney, Agent, or FirmObl0n, Fisher, Spivak, Mc- 22 Filed: Feb. 14, 1973 Clella'nd & Maler Appl. N0.: 332,499

Foreign Application Priority Data Feb. 18, 1972 Japan 47-19424[U] us. c1 315/3971, 315/3951, 335/211 1111. c1. H01j 25/50 Field of Search 315/3951, 39.71; 335/211 1 References Cited UNITED STATES PATENTS 6/1971 Numata 3l5/39.7l

Mims 3l5/39.7l

[5 7] ABSTRACT A magnetron includes an oscillating section having an electron radiating cathode and a cylindrical anode; an output section having an antenna inserted therein; and

.a pair of doughnut-shaped magnets disposed one on the end surface of the anode and one on the other end surface thereof in a manner to be coaxial with the anode. Between the end surfaces of the oscillating section and the magnets a pair of shim plates are arranged. The shim plate has a plurality of projections point-contacted with the magnet.

4 Claims, 2 Drawing Figures QATENTEDMAY 7 .974 3309.950

FIG

FIG. 2'.

MAGNETRON This invention relates to a magnetron. With conventional magnetrons a heat insulating plate of a poor heat conducting material, magnetic shim plate and doughnut-shaped ferrite permanent magnet are sequentially disposed in face-contact with each other on the end surfaces of an oscillating sectionfThe shim plate is pro vided for effectively directing a magnetic field to an oscillating body section, and the heat insulating plate prevents a heat generated at the oscillating body section y from being transmitted to the permanent magnet,

thereby preventing reduction ofa coercive force of the the oscillating body section is transmitted through the insulating plate to the permanent magnet. Furthermore, the heat insulating plateis made of a nonmagnetic material and a magnetic field of the permanent magnet is shielded by the heat insulating plate with the ,result that a sufficient magnetic field does not effectively act on the oscillating body section.

This invention is directed to the solution of such drawbacks. That is, this invention is to provide a magnetron of such a type that a heat generated at an oscillating body section is prevented from being transmitted to magnets and a magnetic field from the magnet can effectively act on the oscillating body section.

A magnetron according to this invention includes an oscillating body section having an electron radiating cathode having one end secured by a stem and arranged in a predetermined axis, an antenna section extending in a predetermined direction from the other end of the cathode in a manner to oppositely facing the stem, and a cylindrical anode coaxially surrounding the cathode and having a plurality of blades constituting a resonance cavity; a pair of magnetic shim plates disposed one at one end surface of the oscillating body section and one at the other surface thereof and having a plurality of projections; a pair of annular permanent magnets disposed one above one end surface of the shim plate and one above the other end surface of the shim plate in a manner. to be abutted on the projections of the shim plates; a radiator provided around the periphery of the oscillating body section; and yokes encasing or housing the magnets and the oscillating body section. With the structure so arranged the oscillating body section is point-contacted with the projections of the shim plates to prevent a heat generated from the oscillating body section from being transmitted to the magnets. As a result, reduction of a coercive force of the magnet by the heat can be prevented. Furthermore since the shim plate is made of a magnetic material, a magnetic field of the magnet can effectively act on the oscillating body section.

This invention is now explained with reference to the accompanying drawings, in which:

FIG. 1 is a view ofa magnetron according to one embodiment of this invention; and

FIG. 2 is a cross section of the magnetron as taken along line 2-2 of FIG. 2.

Referring to FIGS. 1 and 2 conjointly, an oscillating body section 11 has a cathode 12, cylindrical anode 13 and magnetic pole 14. To the inner wall of the cylindrical anode 13 are fixed a plurality of blades 15 extending in the neighborhood of the cathode 12. The plurality of blades constitute a cavity resonator. Around the outer periphery of the cylindrical anode, for example, a laterally blown type radiator 16 is mounted. On the top end of the cylindrical anode a cathode stem is sealingly mounted through a first annular body 17. On the bottom end of the cylindrical anode an output glass window 20 is sealingly mounted through a second annular body 19. Within the output window 20 an antenna 21 led out from the blade 15 extends. Doughnutshaped shim plates 22 and 23 made of magnetic material are disposed on the top and bottom surfaces of the first and second annular bodies 17 and 19, respectively. The shim plates each have a plurality of projections, for example, three. Arranged one above the shim plate 22 and one above the shim plate 23 are a pair of doughnutshaped ferrite magnets 25 and 26 whose one surface is abutted on the projections of the shim plates 22 and 23. A plate-like yoke 27 and a substantially C-shaped yoke 28 are disposed in contact with the other surface of the magnets 25 and 26 respectively. These yokes 27 and 28 are secured by bolts 29 to establish a magnetic circuit. The cathode stem 18 is connected with a series circuit of a choke coil 30 and through type capacitor 31 to prevent a leakage of microwaves. A multi-porous shield case 32 is disposed on the plate-like yoke 27 to encase the choke coil 30 and capacitor therein.

According to a magnetron so constructed the oscillating body section 11 is contacted through the projection 24 with the magnets 25 and 26 to permit a heat from the oscillating body section to be transmitted through the projection only. As a result, a heat conduction to the magnets is reduced to a considerable extent. Between the magnets 25 and 26 and the shim plates 22 and 23 there are provided clearances d1 and d2 corresponding to the projections 24 of the shim plates 22 and 23. The clearances d1 and d2 act as a heat insulator with the result that a heat insulating effect on the magnets is doubled. When the clearances d1 and d2 are created to be of the order of 0.5 mm to 1.0 mm, then magnetic fields from the magnets 25 and 26 act on the magnetic pole 14 of the oscillating body section without involving any attenuation.

According to this embodiment a cooling air is blown through the radiator 16 to permit the oscillating body section to be cooled as well as through the clearances between the magnets and the shim plates to allow the cathode stem 18, choke coil 30 and output window to be cooled. As a result, any adverse effects of a heat on the members of the magnetron can be minimized.

What is claimed is:

1. A magnetron comprising an electron radiating cathode having one end secured by a stem and arranged in a predetermined axis; an antenna section extending in a predetermined direction from the other end of the cathode in a manner to oppositely confront the stem; a cylindrical anode coaxially surrounding the cathode and having a plurality of blades constituting a resonance cavity; a pair of permanent magnets disposed one on one end surface of the anode and one on the other end surface thereof in a manner that said antenna section extends through the-central portion of said one permanent magnet; a pair of shim plates disposed between the magnets and the end surfaces of the I anode and having a plurality of point-contacted projec' tions contacted with the magnets.

2. A magnetron according to claim 1 in which an air projections are provided on each of the shim plates. clearance is created between the permanent magnet 4. A magnetron according to claim 1 in which said and the magnetic shim plate. projections are 0.5 mm to 1.0 mm in height.

3. A magnetron according to claim 1 in which three 

1. A magnetron comprising an electron radiating cathode having one end secured by a stem and arranged in a predetermined axis; an antenna section extending in a predetermined direction from the other end of the cathode in a manner to oppositely confront the stem; a cylindrical anode coaxially surrounding the cathode and having a plurality of blades constituting a resonance cavity; a pair of permanent magnets disposed one on one end surface of the anode and one on the other end surface thereof in a manner that said antenna section extends through the central portion of said one permanent magnet; a pair of shim plates disposed between the magnets and the end surfaces of the anode and having a plurality of point-contacted prOjections contacted with the magnets.
 2. A magnetron according to claim 1 in which an air clearance is created between the permanent magnet and the magnetic shim plate.
 3. A magnetron according to claim 1 in which three projections are provided on each of the shim plates.
 4. A magnetron according to claim 1 in which said projections are 0.5 mm to 1.0 mm in height. 